Many packaging applications, especially food packaging, require or benefit from the use of bags made from various thermoplastic materials and structures. Examples of commercial bags include heat shrinkable bags supplied by Cryovac, Inc., including the "L", B110, and B2550 bags.
These bags are commonly used in large scale meat processing and/or packaging systems where production speed and efficiency are important. Bags to be used in these systems are often themselves packed in boxes, the individual bags taped together so that they will feed in a predictable and efficient manner to an article loading station. Typical of such technology is U.S. Pat. No. 3,161,347 (Hannon), disclosing a tape to which bags are attached, and U.S. Pat. No. 3,587,843 (Wing), incorporated herein by reference in its entirety, disclosing two tapes to which are attached imbricated (i.e. shingled) bags.
At the loading station of a conventional system, each bag is opened and then loaded with an article such as a fresh red meat subprimal or smoked and processed meat, poultry, cheese, or other perishable food product, or other product.
In opening such bags, a problem sometimes encountered is that of bag lips ( the edges of the bag panels which form the bag mouth or opening) which can be undesirably stuck together, or stuck to the adhesive bag tapes. This occurs in conjunction with the use of adhesive tapes to hold a series of imbricated (shingled) bags. Lateral movement of the top ply of the lead bag relative to the bottom ply can cause the top ply of the bag to adhere to the adhesive tape, making it difficult to open the bag. This can create a significant slow-down in a packaging line, and down-time for the food processor or other user of bags. The bags can of course be opened manually, but this is very slow and labor intensive. It also risks unnecessary handling of the bag.
Some solutions have been offered to deal with the problem of opening a bag prior to the insertion of an article into the bag. The use of air pressure is common, but of course requires a source of air pressure. Sometimes the use of air pressure is unpredictable in providing consistent bag opening performance, and the operator sometimes still needs to manually start the opening process so that the air can be effective in further opening the bag sufficiently to allow an article to be loaded therein.
Another problem inherent in conventional bag loading systems is the requirement to match center to center tape spacing to the bag size and article cross section. "Tape spacing" here refers to the pair of adhesive carrier tapes, e.g. as described in the '843 Wing patent, which in many commercial bag loading systems hold bags together in an imbricated manner before loading with an article. Currently, the nature of the tape spacing will generally define the shape of the bag when it is opened. Since the bag dimensions are ideally matched to the dimensions of the article to be packaged, tape spacing is an important parameter in loading a bag with an article.
It is desirable to provide a method and apparatus which lessen or eliminate the requirement of opening the bag manually, or of using air pressure. It is also desirable to provide a method of opening the bag in a reliable and consistent manner, which allows for increased automation, and potentially reduces operating costs.
Likewise, it is desirable to provide a method and apparatus which lessen or eliminate the requirement of matching tape spacing to article size, i.e. the requirement of optimizing tape spacing for feeding or indexing the bags.
Another problem often encountered in the packaging of food products is that the corners of each bag tend to curl over during bag advance and loading. This can sometimes complicate or slow the bag loading process. By finding a way to widen the tape spacing, that is, by placing the tapes closer to the bag's respective lateral edges, without being unduly limited in the need to match tape spacing to bag and article size, this problem is lessened or eliminated.
In transporting bags mounted on a tape, in conventional systems, a discharged package (i.e. a product such as a fresh red meat packaged in a bag) is required to travel over the bag train, i.e. a plurality of imbricated bags mounted on tapes. A disadvantage of such a system is that bags can be knocked off the bag train by the packaged product as it is transported. Another problem common in conventional systems is that the packaging machine takes up a significant amount of floor space. In processing plants, where floor space is at a premium, this can be an important factor. It is desirable to provide a method and apparatus which reduces or eliminates the problem of bags being knocked off the bag train by packaged products, and which reduces the overall floor length of the machine, preferably without sacrificing the ability to horizontally load.